Technical Field
The present invention relates to a failure inspection system for inspecting leakage of a DC power source, and for inspecting a short-circuit failure of switches provided between the DC power source and an electrical apparatus.
Related Art
There is known a failure inspection system having a pair of power lines which connect a DC power source to an electrical apparatus, switches provided in the power lines, and a judgement section which judges whether or not there is a leakage current failure of the DC power source or a short-circuit failure of a switch (see JP-A-2015-065143).
The failure inspection system includes capacitors that are coupled between the power lines and ground, each capacitor disposed at a position of a power line which is closer to the electrical apparatus than the switch is. The failure inspection system also includes a signal generating section which generates an AC signal, and a measurement section which measures the voltage of the AC signal. The signal generating section and the measurement section are provided at a position which is closer to the DC power source than the switch is. When there is a short-circuit of a switch, the AC signal generated by the signal generating section passes through the switch, and flows through a capacitor to ground, and thus the voltage of the AC signal as measured by the measurement section becomes lowered. The judgement section judges, for example, that there is a failure when the measured voltage of the AC signal falls below a predetermined threshold.
Furthermore, when a leakage current failure occurs in the DC power source, the AC signal generated by the signal generating section passes through the leakage position, and flows to ground, so that the measured value of voltage of the AC signal is reduced.
Hence, in this case too, if the measured value of voltage of the AC signal falls below a predetermined threshold, it can be judged that a failure has occurred.
However, the above failure inspection system suffers from a problem that the occurrence of a leakage current failure cannot be distinguished from the occurrence of a short-circuit failure. That is to say, when a leakage current failure occurs, the AC signal flows to ground through a leakage current position, so that the measured value of AC signal voltage becomes reduced. When a short-circuit failure of a switch occurs, the AC signal flows to ground through the switch and a capacitor so that again, the measured value of AC signal voltage becomes reduced. Thus, the measured value of the AC signal voltage decreases in either case, so that it is impossible to distinguish between the two types of failure.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a failure inspection system that uses an AC signal to determine which of two types of failure has occurred, specifically, a leakage current failure or a short-circuit failure.